DE 103 19 947 A1 describes a device for measuring the surface contour of rotationally symmetrical workpieces. A light source and an optical sensor are arranged oppositely relative to the workpiece to be measured, such that the workpiece can be positioned in the light beam. In this way, a measurement of transmitted light is possible.
A measurement device for transmitted light measurement is also described for example in DE 36 30 702 A1. The workpiece can be clamped on a carriage, which is movable along the workpiece axis. The workpiece can thus be moved along its longitudinal axis through the light path between a radiation source and a radiation detector, and the shadowing can be measured. From this, the axial and radial dimensions of the workpiece can be determined.
In the testing device described in DE 40 30 994 A1 for rotationally symmetrical workpieces, a mechanical probe and an optical measurement device are provided. These are arranged opposite one another in the radial direction with respect to the rotationally symmetrical workpiece to be measured. A position for the optical measurement device is determined so that the workpiece dips, up to one half, into the produced beam strip of the optical measurement device. The beam strip is oriented at the contour of the workpiece parallel to the tangential direction at the measurement point. Since the workpiece dips up to one half into the beam strip, the measurement of the contour of the workpiece will be taken at the point with the sharpest imaging, thus enabling an accurate measurement.
Various optical measurement devices are known from the prior art for measuring shafts. The applicant for example markets optical measurement machines of the “MarShaft Scope” type, with which shafts can be measured. Such optical measurement devices can have two optics units, specifically a lighting unit and a receiving unit, for example so as to measure a shaft or another object in the transmitted light. It is also known to use telecentric optics units for this purpose, since with telecentric optics units size can be determined independently of the distance from the object.
A number of challenges still exist in practice. Even with the use of a telecentric receiving unit and a telecentric lighting device, measurement inaccuracies can occur, which in particular have an effect when a length measurement is to be taken between two planar surfaces of the shaft, for example on a planar surface at which two cylindrical portions of the shaft of different diameter contact one another. A further challenge lies in the fact that measurement errors arise when the optical axes of the optics units are inclined relative to one another and/or are offset from one another.